In the multi-piece valve disk of a double seat valve known from DE 101 47 455 C, which comprises two valve disks each cooperating with the inner wall of a seat with a sliding valve function, the ring seal consists of three prefabricated components mounted into each other, namely of the sealing ring of an elastomeric material, the dimensionally stable backup ring, and the restoring region for the sealing ring inserted in-between, for example in the form of an O-ring. As the backup ring is supported only radially at a portion of the valve disk, the clamping width of the ring groove receiving the ring seal, which generates the preload frictional connection for the sealing ring, is only defined by the metallic contact between the parts of the valve disk screwed to each other. The backup ring is seated axially floating between the outer sides of the sealing ring. Due to the manufacturing tolerances of the valve disk parts, it is difficult in this concept to adjust a defined clamping width for the ring groove that can be exactly reproduced and is decisive for an exactly defined preload frictional connection of the sealing ring with the ring seal being mounted and for its proper functioning during the operation of the double seat valve. When the double seat valve is in operation, i.e. when the valve disk is shifted along the inner wall of the seat with the external sealing zone being dynamically deformed, when the sealing ring emerges from the seat, and when the sealing ring submerges again in the seat, in each case with a flexing deformation of the external sealing zone, inevitable relative motions between the three components occur and lead to local concentrations of friction, stress concentrations and flexing movements in the sealing ring, resulting in a limited service life of the sealing ring. These mechanical influences are even intensified by possible floating movements of the backup ring in the axial direction between the clamped outer sides of the sealing ring.
In a double seat valve known from EP 1 730 430 A, the one valve disk provides a seat valve function on a conical face of the seat, while the other, multi-piece valve disk provides a sliding valve function with an only radial sealing in the seat. The ring seal in the multi-piece valve disk consists of an elastic sealing ring with an approximately C-shaped cross-section and a backup ring with an approximately T-shaped cross-section, where the sealing ring is vulcanized onto the backup ring, such that a radial external sealing zone adjacent to the T-crossbeam of the backup ring and additionally an axial central sealing zone in the upper side of a part of the valve disk are exposed. The manufacture of the ring seal embodied as composite structure is complicated and expensive. As the sealing ring is exposed at two adjacent sealing zones, it requires the connection with the backup ring by vulcanization, as otherwise an outer side of the sealing ring could perform inadmissible relative motions during which a cleaning medium or a working medium would get behind the ring seal. However, the backup ring defines the clamping width of the ring groove as the parts of the valve disk are positively supported at the backup ring and position it axially.
It is one aspect of the disclosure to improve a multi-piece valve disk of the type mentioned in the beginning as well as a ring seal with respect to an inexpensive and easy manufacture, high functional reliability and a minimum number of components.
As the ring seal in the multi-piece valve disk only consists of two components and during the operation of the sliding and/or seat valve, relative motions thus only occur, if they do occur at all, between two components, the result is a cheaper manufacture, simple assembly, comfortable disassembly when the sealing ring, being an expendable part, is exchanged, and a higher functional reliability.
The ring seal is a functional and universal equipment component of such valve disks as the backup ring takes care of a defined positioning of the sealing ring and supports an exactly predetermined preload frictional connection.
According to the disclosure, parts of the valve disk are positively and non-positively supported at the backup ring from two sides in axial directions defined by the stroke direction of the valve disk, so that the backup ring is positioned stably and cannot perform any relative motions relative to the sealing ring. By the support of the parts at the backup ring, the clamping width of the ring groove between the parts of the valve disk generating a preload frictional connection for the sealing ring is thus defined. In this manner, a largely constant preload of the sealing ring in the ring groove can be ensured within one line of valve disks and ring seals, where manufacturing tolerances, for example of the threaded connection between the parts and/or the tightening torque of a threaded joint, do not have any influence on the preload of the sealing ring.
According to the disclosure, by a radial support at a part of the valve disk, the backup ring furthermore defines the radial position for the sealing ring generating a protrusion of the external sealing zone of the sealing ring over the valve disk, so that the backup ring can thus fulfill a further positioning function in the ring seal or the valve disk, respectively.
Corresponding to a particularly important independent idea of the disclosure, different backup rings are used which differ in that the indentation either faces radially outwards or has an axial orientation, or is even oriented obliquely outwards with axial and radial direction components. These backup rings permit to make ring seals which can be optionally used for valve disks having different valve functions, e.g. for a valve disk with an only radial sealing and a sliding valve function, a valve disk with a radial and an axial sealing with a seat valve function, or a valve disk with an only axial sealing and also with a seat valve function. The orientation of the indentation present in the different backup rings thus determines the application of the respective backup ring for the ring seal of the respective valve disk type. This idea is particularly suitably expanded by employing, independent of the embodiment of the backup ring, always the same type of sealing ring which is placed onto the two backup rings in different rotational positions, but can be produced in one and the same manufacturing mold. This philosophy of identical parts has a further advantageous influence on the producing costs at least of the sealing rings (large piece number) and thus also of different valve disks. Another advantage of this concept is that the risk of confusions during the manufacture or assembly of the valve disks and during a replacement of a backup ring is minimized as only the respective correct backup ring can be installed anyway, and the sealing rings having the same shapes and dimensions and which can be combined with the respective backup ring fit in any case.
According to the disclosure, the same type of sealing ring can be even placed onto each of the different backup rings, i.e. each of the sealing rings manufactured in the same production mold with one single specification.
As, depending on the embodiment, i.e. the shape and/or size of the respective backup ring, the placed sealing ring is optionally extended and/or rotated to a greater or lesser extent, according to the disclosure, the same type of sealing ring can be used and can be manufactured in the same production mold, but optionally with a different Shore hardness or elasticity, or from different materials. Such internal differences between the externally identical sealing rings can be easily realized in the manufacture of the sealing rings, for example in injection molding.
In one suitable embodiment, the sealing ring has two outer sides in its cross-section where preferably their thickness increases towards their free ends, so they are, for example, approximately designed like a wedge. Between the outer sides, the external sealing zone, preferably designed like a roof, is provided at the outer surface. At the inner surface, a ring groove is shaped adjacent to each outer side. Between the ring grooves, the sealing ring finally comprises at least one annular ring projecting to the inside. The annular ring can be designed with an at least partially circular cross-section. This simple cross-sectional shape of the sealing ring satisfies the different requirements in view of the sealing and working characteristics during the operation of a sliding or seat valve and can be produced at low costs. The material of the sealing ring can be an elastomer or rubber.
In one suitable embodiment, the backup ring comprises a base part limited by backup surfaces orthogonal with respect to each other, two spaced ring ribs projecting in parallel perpendicularly or obliquely from the base part and fitting into the ring grooves of the sealing ring, and the indentation between the ring ribs embodied as a ring groove. The backup ring can consist of metal or of a material that is harder than the material of the sealing ring. The indentation can be embodied as approximately rectangular ring groove, or as a semi-circularly fluted ring groove. The backup ring can be manufactured easily and at low costs. The ring seal can be comfortably mounted.
In one suitable embodiment, the ring ribs can be offset in the backup ring inwards with respect to the base part via external shoulders. With a relatively broad base part which provides high stability of the backup ring and its defined positioning, nevertheless a relatively great amount of material can be accommodated in the outer sides of the sealing ring in the ring groove and statically preloaded in this manner. Moreover, the external shoulders offer the possibility of providing clearances for the “expansion” of the outer sides of the sealing ring due to swelling and/or temperature conditions.
In another suitable embodiment, with the ring seal being mounted in the valve disk, open alternative spaces for the outer sides and/or the annular ring are provided between the parts of the valve disk lying against the backup ring and the backup ring, and optionally even in the indentation, these spaces ensuring a deformation characteristic of the sealing ring mounted under a preload which can be relatively exactly predetermined and largely remains constant despite temperature and possibly swelling influences.
To facilitate the assembly of the ring seal, in one suitable embodiment, the backup ring can be divisibly embodied of ring segments. When the sealing ring is being placed, it does not have to be expanded inappropriately, but the segments are inserted in the sealing ring and then joined inside in the sealing ring. In the mounted state, i.e. fixed by the adjoining parts of the valve disk, the divided backup ring nevertheless acts like an integral backup ring.
Due to the simple assembly of the two components resulting in the ring seal, the sealing ring can be embodied with a Shore hardness of about 85 Shore, i.e. relatively hard, whereby in the mounted state, it is largely prevented that a cleaning medium and/or an operating medium gets behind the ring seal, and/or that the latter is torn out of the ring groove.
As the demands on the sealing characteristic of the sealing ring differ in different areas of its cross-section, it can be suitable to fabricate the sealing ring with bi-injection molding technology in one piece, but with zones of different Shore hardnesses and thus elasticities, or from different materials. This two or multi-component technology is well-known and in the present case permits to individually adapt the sealing ring selectively to the requirements to be expected in the respective areas of its cross-section, e.g. to static and dynamic sealing functions.
Though the sealing ring could be adhered to the backup ring, an embodiment is preferred in which the sealing ring is attached such that it can be exchanged. This is because the sealing ring is an expendable part of the valve disk and optionally has to be exchanged, while the backup ring is kept after the sealing ring has been replaced and exactly ensures the predetermined preloading relations for the new sealing ring.